| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 8.56 | 68 |
| 2015 | 8.83 | 79 |
| 2014 | 9.06 | 82 |
| 2013 | 9.3 | 83 |
| 2012 | 9.42 | 77 |
| 2011 | 9.43 | 83 |
| 2010 | 9.53 | 82 |
| 2009 | 9.79 | 80 |
| 2008 | 10.25 | 77 |
| 2007 | 10.28 | 77 |
| 2006 | 10.63 | 77 |
| 2005 | 11.64 | 73 |
| 2004 | 12.92 | 73 |
| 2003 | 12.35 | 77 |
| 2002 | 13.3 | 72 |
| 2001 | 13.98 | 72 |
| 2000 | 14.68 | 69 |
| 1999 | 16.06 | 66 |
| 1998 | 17.16 | 65 |
| 1997 | 17.9 | 63 |
| 1996 | 19.33 | 60 |
| 1995 | 19.6 | 59 |
| 1994 | 19.47 | 60 |
| 1993 | 19.31 | 58 |
| 1992 | 21.33 | 52 |
| 1991 | 24.03 | 47 |
| 1990 | 26.58 | 43 |
| 1989 | 24.61 | 41 |
| 1988 | 25.24 | 40 |
| 1987 | 26.32 | 38 |
| 1986 | 26.64 | 35 |